U.S. Patent No. 5,297,516, issued on Mar. 29, 1994 discloses a VVA apparatus that employs a main rocker shaft supporting a main rocker arm. The main rocker arm supports a sub-rocker shaft for a sub-rocker arm. A lost motion mechanism disposed between the main rocker arm and the sub-rocker arm is operable unless a lever on the main rocker arm is locking engagement with the sub-rocker arm. The lost motion mechanism includes a spring-biased plunger that rests on an exposed portion of the main rocker shaft. According to this known apparatus, the cylindrical outer peripheral surface of the main rocker shaft serves as a plunger seat and thus the main rocker arm is not formed with any appropriately designed plunger seat for the lost motion mechanism.
An object of the present invention is to improve the variable valve actuation apparatus according to the prior art such that the cylindrical outer peripheral surface of the main rocker shaft is not used as a plunger seat for the lost motion mechanism.